Ingredients:
1 quart chicken stock or vegetable stock
2 stalks lemon grass, white part only, cracked open with the flat side of a knife
3 kaffir lime leaves, fresh or dried, hand torn
1 (3 inch) piece of fresh ginger, peeled and thinly sliced
2 small Thai chilies, halved lengthwise
2 garlic cloves, crushed
2 (13 oz) unsweetened coconut milk
2 T Thai fish sauce (nam pla in some stores)
1 1/2 t sugar
1 (8 oz) can straw mushrooms, rinsed
4 limes, juiced
1 1/2 C cubed cooked chicken
Kosher salt and freshly ground pepper
1/4 C chopped fresh cilantro leaves

Directions:
Bring the stock to a boil over medium heat in soup pot. To make things easier, we added the lemon grass, kaffir lime leaves, ginger, chilies, and garlic into a cheesecloth to remove them easier. Lower the heat to medium-low, cover, and gently simmer for 10 minutes to let the spices infuse the broth. Remove the cheesecloth and squeeze the juice out of it into the soup and throw it away (or just strain all the spices out if you didn't use the cheesecloth).
Uncover and stir in the coconut milk, fish sauce, sugar, mushrooms, lime juice, and chicken. Simmer for 5 minutes to heat the chicken through; season with salt and pepper. Garnish with cilantro. Be careful to avoid chewing lemongrass, ginger or lime leaves.